Automatically add missing / to routes

[Mechite]

When you define an @OpenApi annotation anywhere and haven't added a preceeding "/" to a path (i.e. path = "test" vs path = "/test"), when trying to use ReDoc, small issues occur where ReDoc doesn't expect there not to be a preceeding slash and formats the documentation wrong. This is more of a ReDoc issue, but can't hurt to fix it with some processing.